Paraffin deposition control



United States Patent 3,416,605 PARAFFIN DEPOSITION CONTROL Byron E. Marsh, Western Springs, and Roy J. Betty, In,

Chicago, Ill., assignors, by mesne assignments, to Armour Industrial Chemical Company, a corporation of Delaware No Drawing. Filed June 30, 1967, Ser. No. 650,262

11 Claims. (Cl. 16638) ABSTRACT OF THE DISCLOSURE A method of controlling paraffin deposition in oil field and associated operations by addition of urea or polyurea formed by the reaction of an amine and an isocyanate.

Background Paraffin deposition has been a serious problem in many phases of the oil industry for years. Paraffin-like hydrocarbon material contained in petroliferous fluids, include high molecular weight aliphatic hydrocarbons, resins, asphaltic materials, aromatic hydrocarbons, and naphthalene which may deposit together with oil, inorganic scale, water and sand causing accumulations which reduce the flow in well formations, well tubing, flow lines from Wells to tanks, and the like. The parafiin deposits may vary from one crude oil type to another, from one well to another, and in various geographical locations.

The deposition of paraffin-like materials contained in petrolifcrous fluids in a natural occurrence which is enhanced by colder temperatures when the paraffins are likely to precipitate from the oil. Many methods have been used in attempts to overcome the problem of paraffin deposition in oil well tubings, accessory surface level piping and storage tanks. Various heating methods utilizing electrical and chemical heating methods have been used to heat the oil to redissolve the paraffin. Mechanical boring of well tubing and mechanical cleaning the surfaces of tanks and pipes has been resorted to in order to remove paraffin deposits. Various chemical treatments have been proposed, such as solvents to remove deposits as described in US. Patent 3,162,601; various chemical methods of coating petroleum conduits and containers to prevent or retard paraffin deposition such as described in U.S. Patent 3,249,535; and the use of certain amino acid parafiin deposition inhibitory agents such as described in U.S. Patent 3,102,859. It is understood that it would be preferable to prevent the deposition of paraffin from the petroliferous fluid at all stages from the well formation through the well tubing, associated piping and storing facilities until the crude oil is further processed.

Summary of the invention This invention is directed to a method of controlling the deposition of paraflin from petroliferous fluids by introducing into such fluids or forming in situ in such fluids a urea or a polyurea to substantially retain the paraffinic materials in suspension or solution in the hydrocarbon fluid and thus prevent paraffin deposition from taking place. These agents .may be introduced to the oil fluids at any stage of production from being added to or formed in situ in the producing formation to addition to storage tanks containing crude oil.

Ureas and polyureas suitable for use in our invention may be formed by the reaction of aliphatic amino compounds with aromatic and aliphatic isocyanates and polyisocyanates respectively. Mixtures of amines and monoand polyisocyanates may be used. The amine terminated structure is preferred for control of paraffin deposition.

Aliphatic amino compounds are preferred amine reactants, particularly amines containing an aliphatic group of from about 6 to 22. carbon atoms attached to an amino nitrogen. Such aliphatic groups may be branched or straight chain and saturated or unsaturated. Primary monoamines selected from the group consisting of N- normal-alkyl and N-secondary-alkyl amines wherein said alkyl group contains from 6 to about 22 carbon atoms are preferred. N-secondary-alkyl amines are especially useful due to their low melting points. One preferred subclass is N-secondary-alkyl amines having from about 7 to 18 carbon atoms. When aliphatic diamines are used, the amino functions are preferably connected by an alkylene radical having from 2 to 14 carbon atoms and the diamine contains an aliphatic group of from about 6 to 22 carbon atoms attached to an amino function. Preferred diamines include N-alkyl trimethylene diamines wherein the aliphatic group may be primary, secondary, and tertiary alkyl, aminostearylamine, and aminomethylstearylamine. The aliphatic group may be a cyclic group or an arylalkyl group such as is present in the'amine derived from phenylstearic acid, or it may be an amino substituted group resulting in tetra-amines such as N,N-(otaminopropyl)-aminostearylamine and N,N-(a-aminopropyl)-aminomethylstearylamine.

Isocyanates suitable for the process of this invention includes those isocyanates which react with an amine to form a urea or polyurea. Long chain aliphatic isocyanates are suitable wherein the aliphatic group contains from about 6 to 22 carbon atoms. It is preferred to use difunctional isocyanates, or pre-polymers thereof, including diisocyanates such as toluene diisocyanate, hexamethylene diisocyanate, and long chain aliphatic diis0- cyanates such as derived from aminostearylamine and aminomethylstearylamine.

The amine terminated polyurea may be formed by using an excess of amine in an amount of from about 1.1 to 3.0 equivalent moles of diarnine per mole of diisocyanate. The number of repeating units of the amine terminated polyurea may vary from 1 to about 5 0. The urea or polyurea may be formed by adding the amine and isocyanate to a liquid medium with suflicient stirring to assure contact for reaction. It is preferred to add the amine and isocyanate reactants to kerosene, diesel oil or other petroleum soluble liquid to form the urea or polyurea in situ in the liquid. The in situ formation of the urea or polyurea in a fluid such as kerosene increases the viscosity of the fluid and forms a thixotropic gel. For example, a 10 percent active gel of in situ reacted amine and diisocyanate may be formed. While it is preferred to introduce the urea or polyurea into the oil well fluid in the form of an in situ formed gel of a petroleum soluble liquid, it is obvious that, for instance, percent active urea or polyurea may be finely ground and added to the oil well fluid, or the urea or polyurea may be formed in the petroleum fluid by addition of the amine and isocyanate separately as described in copending U.S. patent application, Ser. No. 650,227, entitled Oil Well Treatment filed on even date herewith. The urea or polyurea may be added at any stage of petroleum production, but if it is added at the bottom of the well bore, paraflin deposition will be controlled in the well bore tubing as well as in accessory surface pipe lines and tanks. In some cases, it is desirable to add additional urea or polyurea to surface lines and storage tanks as, for example, during cold weather.

Urea or polyurea, which will effectively control paraffin deposition, may also be represented in crude petroleum pumped from oil wells as the result treatment of the Well with an amine and an isocyante to form urea or polyurea in situ as a well treatment to control water coming, render the producing formation preferentially oil wettable, consolidate sand formations, prevent clay swelling and the like. This method of treatment is described in copending U.S. patent application, Ser. No. 650,227, entitled Oil Well Treatment filed on even date herewith.

The amount of chemical suitable for use in the treatment method of our invention varies over wide ranges and may vary with the nature of the petroleum liquid and well conditions encountered. In general, it is preferred to employ more than 10 p.p.m. of the urea or polyurea on the basis of the crude petroleum. The upper limit of the amount of chemical employed according to this invention is not critical, but from practical considerations, from about 10 p.p.m. to 10,000 p.p.m. are suitable. Concentrations from about 50 to 5,000 p.p.m. produced especially good paraflin deposition control under normal conditions.

The following examples are presented to illustrate this invention.

Example I Kerosene gels were formed by the in situ reaction of the noted amine with toluene diisocyanate using 2 moles of amine per mole of toluene diisocyanate. The noted amounts of kerosene gel were added to 100 mls. of kerosene in 150 ml. beakers. The beakers were warmed and the noted 2 or 10 percent paraflin wax was added to each beaker and the heating continued until the paraflin dissolved in the kerosene. The beakers were maintained at 150 F. for 15 minutes and then at 110 F. for 15 minutes. The beakers were then maintained at room temperature and observed for paraflin wax crystallization on the sides of the beakers. The beakers were reheated as above to solubilize the paralfin and then maintained at 0 F. and again observed for paraffin wax deposition. The results are shown in Table I.

TABLE I Percent paraffin Conc. Parafiin wax suspended Chemical (amine) (p.p.m.) wax (percent) Room 0 F.

temp.

None (control) 2 0 0 N-sec-alkyl(C -v) amine 50 2 100 0 100 2 100 50 N-sec-alkyl (Ci-10) a1nine 50 2 100 50 100 100 50 N -sec-alkyl (Cn-n)amine 50 2 100 50 100 2 100 50 N -sec-a1ky1 (On-2o) amine 50 2 50 0 1, 000 2 50 0 N -cocoamine 2 50 2 50 0 1, 000 2 50 0 N-oleylamine 3 50 2 50 0 1,000 2 50 0 1 Amines obtained by amidation of 0 -0 cut of a-olefins.

Amines obtained from coconut sources containing saturated and unsaturated hydrocarbon groups from 010 to C15.

3 Amines obtained from oleic acid.

The above data clearly show the effective control of parafiin deposition in kerosene by the addition of kerosene gel obtained by the in situ reaction of toluene diisocyanate with the noted amine.

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

We claim:

1. A method of controlling deposition of paraflin contained in petroliferous fluids in subterranean formations surrounding a well bore, and oil well tubing, and associated surface piping and storage tanks, comprising adding to said fluids a compound selected from the group consisting of urea and polyurea formed by the reaction of an amine containing an aliphatic group of from about 6 to 22 carbon atoms attached to an amino nitrogen and an organic isocyanate.

2. The method of claim 1 wherein more than 10 p.p.m. of said compound on the basis of said petroliferous fluids are added to said fluids.

3. The method of claim 2 wherein irom about 50 to 5,000 p.p.m. of said compound is added to said fluids.

4. The method of claim 1 wherein said isocyanate is a diisocyanate.

5. The method of claim 4 wherein said diisocyanate is an aliphatic diisocyanate.

6. The method of claim 4 wherein said diisocyanate is toluene diisocyanate.

7. The method of claim 1 wherein said amine is a primary monoamine selected from the group consisting of N-normal-alkyl and N-secondary-alkyl amines wherein said alkyl group contains fro-n1 6 to about 22 carbon atoms.

8. The method of claim 1 wherein said amine is N- secondary-alkyl amine and said isocyanate is toluene diisocyanate.

9. The method of claim 8 wherein said amine is N- sec.-alkyl(C amine, and said urea is added in a petroleum soluble gel.

10. The method of claim 1 wherein said amine is N- sec.-alkyl-trimethylenediamine and said isocyanate is toluene diisocyanate.

11. A paraflin deposition inhibited petroliferous composition comprising oil and from about 10 to 10,000 p.p.m. of a compound selected from the group consisting of urea and polyurea formed by the reaction of an amine containing an aliphatic group of from about 6 to 22 carbon atoms attached to an amino nitrogen and an organic isocyanate.

References Cited UNITED STATES PATENTS 3,102,859 9/1963 Anderson et a1. 252-83 3,162,601 12/1964 Jones 252-83 3,249,535 5/1966 Keil 252-83 3,342,264 9/1967 Willard l66-38 JAMES A. LEPPINK, Primary Examiner.

US. Cl. X.R. 1664l; 2528.3 

